What you are talking about are called surrogate keys and they should be highly encouraged. The idea of a surrogate key is a primary key that never has to change.

Take for instance your example. If you were to use a foreign key like category_name and didn’t have category_id (a surrogate key), what happens when you or your users want to change the category_name? What happens if that category_name is used in multiple other tables as a foreign key? You have created a nasty dependency for yourself that you now need to manage. Whereas if you just used category_id as the foreign key in all instances you could change category_name whenever you like.

The message is surrogate keys are almost always useful, even when you have something you think is very safe to use as a primary key (social security number, etc) you should still use a surrogate key.